900 gardaí to secure border at G8

Plans have also been drawn up for special courts and extra detention cells at locations in the republic, including counties Donegal and Monaghan, should disorder break out.

The summit of world leaders is taking place at Lough Erne Resort, in Co Fermanagh, on 17 and 18 June and a number of delegations are staying in the south.

And despite UK authorities revealing the cost of the operation to its public purse, Irish taxpayers have been told they will have to wait until afterwards for details of the policing bill.

GardaAssistant Commissioner Kieran Kenny, who is in charge of the border counties, said the force is in close contact with security services in a number of countries as well as international agencies Interpol and Europol.

Daily intelligence briefings are being held on both home-grown and overseas threats.

“For an event of this magnitude, the what-ifs list is endless,” he said.

So, in so far as we can, plans will take account of worst case and best case scenarios

Garda Assistant Commissioner Kieran Kenny

Asst Commissioner Kenny said there are contingency plans to respond to a “mix” of threats, which includes the risk of local dissident republicans using the occasion for global publicity.

But the Garda chief said they had no estimate of numbers of protesters expected into the country at this stage. A large protest is expected in Dublin.

Surveillance of ports and airports across the republic and the movement of people throughout the island will form a major part of the security operation.

Eight temporary border checkpoints are to be manned by Garda units backed up by the Irish Army, alongside rolling checkpoints by mobile patrols.

Asst Commissioner Kenny warned people living along the border and others travelling across it to expect disruption in the run up to and during the summit.

The Garda has also been working with the Courts Service about the possibility of special sittings and custody arrangements, should public disorder break out or in the event of an attack.

Another 3,600 officers from forces around the UK will be drafted in for what is expected to be the biggest ever carried operation carried out by the PSNI.

As part of the huge security operation around the high profile event, a seven-mile stretch of Lough Erne is being closed down completely across three days while the Loughshore Road, Enniskillen, is closed until 26 June.

Authorities in the UK have already revealed they expect the event to cost around £50m.

Asst Commissioner Kenny said the Garda was still in the latter stages of planning and final costs, overseen by the Department of Justice and other Government departments, are not available for taxpayers in the Irish Republic.

“It is a fluid, moving plan. The finer detail of the plan is only coming to light in the latter stages of it, because the countries are voicing their requirements now.”

The Garda chief said the force would give a detailed account of costs after the event.

“Our spending and costs are being challenged on an ongoing basis,” he said.